Benzisothiazolinone Derivatives as Potent Allosteric Monoacylglycerol Lipase Inhibitors That Functionally Mimic Sulfenylation of Regulatory Cysteines.

We describe a set of benzisothiazolinone (BTZ) derivatives that are potent inhibitors of monoacylglycerol lipase (MGL), the primary degrading enzyme for the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG). Structure-activity relationship studies evaluated various substitutions on the nitrogen atom and the benzene ring of the BTZ nucleus. Optimized derivatives with nanomolar potency allowed us to investigate the mechanism of MGL inhibition. Site-directed mutagenesis and mass spectrometry experiments showed that BTZs interact in a covalent reversible manner with regulatory cysteines, Cys201 and Cys208, causing a reversible sulfenylation known to modulate MGL activity. Metadynamics simulations revealed that BTZ adducts favor a closed conformation of MGL that occludes substrate recruitment. The BTZ derivative 13 protected neuronal cells from oxidative stimuli and increased 2-AG levels in the mouse brain. The results identify Cys201 and Cys208 as key regulators of MGL function and point to the BTZ scaffold as a useful starting point for the discovery of allosteric MGL inhibitors.

Peroxide-Dependent MGL Sulfenylation Regulates 2-AG-Mediated Endocannabinoid Signaling in Brain Neurons.

The second messenger hydrogen peroxide transduces changes in the cellular redox state by reversibly oxidizing protein cysteine residues to sulfenic acid. This signaling event regulates many cellular processes but has never been shown to occur in the brain. Here, we report that hydrogen peroxide heightens endocannabinoid signaling in brain neurons through sulfenylation of cysteines C201 and C208 in monoacylglycerol lipase (MGL), a serine hydrolase that deactivates the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG) in nerve terminals. The results suggest that MGL sulfenylation may provide a presynaptic control point for 2-AG-mediated endocannabinoid signaling.